Flight control indicators for providing visual information indicative of aircraft flight parameters are well known. Such flight control indicators include artificial horizons (attitude indicators), turn coordinators, heading and ground track indicators, compasses, pitch indicators, radar and barometric altitude indicators, and a variety of other flight control instruments. Such flight control indicators provide the pilot with critical information regarding the attitude and position of the aircraft so as to facilitate flight safety, even during adverse visual conditions.
As those skilled in the art will appreciate, it is not uncommon to rely upon such instrumentation to properly perform critical flight maneuvers. For example, when the horizon cannot be seen, such as during conditions of low visibility, the pilot's senses cannot distinguish between a banked turn and straight and level flight. In either case, gravity and/or centrifugal force act upon the pilot in a direction normal to the pilot's seat, thus potentially leading the pilot to believe that the aircraft is flying straight and level even when the aircraft is in a banked turn. As those skilled in the art are aware, relying solely upon the pilot's senses has, in the past, led to fatal aircraft crashes.
It is also known to integrate a plurality of such flight control indicators in an attempt to provide a compact and easily read device. U.S. Pat. Nos. 5,250,947; 5,248,968; 5,212,480; 5,136,301; 4,903,017; 4,626,851; 4,583,094; 4,563,742; 4,326,189; 4,419,079; 4,283,705; 4,040,005; 3,970,829; 3,520,994; 3,500,413; 3,162,834 and 2,685,226 disclose examples of such integrated devices.
As those skilled in the art will appreciate, there has been a definite trend in the art during recent years toward the development of heads-up displays wherein the flight control indicators are projected in such a manner as to allow the pilot to view such indicators without lowering his head. Further, it is desirable to provide an integrated heads-up flight control indicator wherein the important individual indicators are integrated into a single display for quick reference.
When using such a heads-up display, the pilot's attention is not momentarily distracted from the field of view. Such momentary distraction is particularly undesirable in military situations, wherein it is critical to continually observe one's surroundings. It is also advantageous to utilize such a heads-up display in many civilian applications. For example, when flying any aircraft at low altitudes, it is very desirable to maintain continuous surveillance of the terrain so as to avoid a collision with upstanding structures, i.e., buildings, radio towers, etc., and natural formations, i.e., mountains, trees, etc. Even the momentary distraction associated with checking the instrument panel has the potential for causing a catastrophe.
Although some of the displays disclosed by the cited prior art patents may appear to be suitable for use as flight control indicators for heads-up displays, it is important to recognize that a properly designed heads-up display will exhibit certain desirable characteristics, which are lacking in such contemporary devices. Most importantly, a properly designed heads-up display will be simple in construction such that it does not distract the pilot from normal viewing through the aircraft canopy or helmet visor and such that the desired information displayed thereby may readily be ascertained. Thus, the indicator must contain the appropriate number of elements which are required to convey the desired information. Any extraneous elements merely unnecessarily complicate the display and distract attention away from those elements which provide crucial information, as well as distract attention away from normal observation through the canopy or helmet visor.
In this respect, it is desirable that the number and configuration of elements be optimized to most effectively and efficiently convey the desired information. It is thus also desirable that elements of the flight control indicator serve a plurality of different indicating functions, where possible.